Organic media for optical recording is known to those of skill in the art. Generally speaking, such media must undergo a detectable change in optical properties when irradiated by a beam of light in preselected areas so that bits of information can be recorded in useful form. The change in optical properties may be a change in reflectivity or refractive index and may be primarily photochemical or thermal in nature or some combination thereof. In any case, a large optical contrast between recorded and unrecorded areas is oftentimes desirable so that differences in optical properties are readily detected without the need for highly discriminating and expensive collateral apparatus.
Organic recording media are typically more suitable for write-once, read-many (WORM) systems because existing organic media tend to undergo irreversible change in optical properties when marked with a laser, for example. The change is irreversible in the sense that the surface cannot, practically speaking, be restored to its original state after marking. It has been reported in the literature that the homogeneity of certain anisotropic films may be reversibly changed by irradiating the surface with light parallel and then with light perpendicular to the optical axis of the film's initial state. Stumpe, J. et al "Photoreaction in Mesogenic Media", Makromol. Chem. Rapid Commun. 12, 81-87 (1991).